Method of preparing fatty acid esters of borneol and isoborneol



' upon the amount of the Patented Mar. 21, 1933 UNITED A B IRATENTorsrcis VALEN TIN HILGKEN, OF GERSTHOFEN, NEAR,AUGSBURG, GERMANY,ASSIGNOR TO I. 'G.

FARBENINDUSTRIE AK .zMZANY mnensnnnsomrr, or

ERHNKFQRT ON-THE MAJN, .GER-

METHOD OF PREPARING FATTY ACID ESTERS 0F BORNEOL .AN'D ISOBORNEOL NoDrawing. Application filed October 19, 1931, S eria13No.1569;843,.m11.:in.ZGermany- NovemberW, 1930.

My present invention relates to an improved method of preparing fattyacid esters of borneol and isoborneol, more particularly to a method ofpreparing the acetic acid ester and formic acid ester.

Fatty acid esters of borneol and isoborneol have hitherto been preparedby causing the corresponding fatty acids to react upon camphene in thepresence of a catalyst, for instance sulfuric acid, phosphoric acid,zinc chloride and the like. This process requires the use of an excessof fatty acid of, for instance, about 470 per cent. and the applicationof an elevated temperature because, otherwise, the yield is rather low.Thereby the disadvantage is esterification process is completed, theexcess of the fatty acid has to be removed by distillation or a washingoperation. The esterification with be performed without the use of acatalyst; however, in this case an excess of 500 per cent. of acid isnecessary. If the esterification is performed with an excess of about 26per cent. of formic acid, there must be applied during theesterification a tempera-v ture which is higher than the boiling pointof the acid.

I have now found that the esterification of camphene with fatty acidscan be considerably improved by using boron trifluoride as a catalyst.In this case the reaction already takes place with a small excess of 20per cent. of fatty acid over the theoretical amount and at ordinarytemperature. This efiect is produced by the application of a smallamount of boron trifiuoride. An amount of about 0.3 to 1 per cent.,calculated camphene, is, for in- The heat evolved during the reactioncan be removed by a cooling operation. It is likewise possible to usecamphene and fatty acid in molecular quantities; however, in this case,the application of an elevated temperature of, for instance,

stance, suitable.

involved that after the,

formic acid may likewise about. 5Q $0. .andaprolonged .timegarenecessary. 5 V

By my new ,process .the advantage is ,involved ;that .theuse -.ofaegreat excess of the fatty .acid .and out ofthe excessof .fatty acidaftenthe a reaction .is completehave -.become-.unnecessany. elllhe newprocess .:-may be applied i in-.th.e preparation of all fatty. acid.esters of borneo'l and soborneol, particularly of ,those of the,propionic. acidetc. 1 a

The. following examples .serve :to illustratethe'invention,:but-they-are not intended to limititthereto: Y

(1) ,.1'0O,grams.of camphene .of .96 per cent. strength, 5.3 ,grams. of,glacial v,acetic. acid of 100 ,percent; strength .Land' l gram of boronatrifluori'de dissolved 'lin a smallguantity .of glacial acetic acid aremixed, whileestirrin the 5 distilling and .washing 55 lower..ac1'ds,.s11ch asrformic .acid, acetic acid,

The liquid .at .first .turbid, very-quickly becomes .c'lear .andjheatslitself .toabout 50 The solution is .allowed .to .stand for some timeatrroomltemperature. ,A fterthe solution has {been washed 7 with water,.951 .per cent; .(i'f fisobornyliacetate,are obtained, cor- .respondingto aneesterificationof.99per gcent. 1(2) ;1i0,0.grams of.campheneof.96, pericent. .-str.ength,250 gramsidfglacial aceticlacidof"IOO'percent. strength and 1 gramofboron trifluorideare mixed,isolutionlheats f itslfslightly. It is allowed .to standzat ordinarytemperature. .After .the solution 'has "been Iwashed .with water,isobornyl acetate .of Q96 pencent. strength is obtained.

3) l'100 ;grams of.camphene of,'97;;per cent. streng'th, 41.5 grams.of..'f0rmic .acid of .99

;.''Z5 .whileagitating. The

per cent. strength zan'dlO-A, gram. ,ofiborontrifluoride are mixed,wliil-e agitating-and .the

mixture is lkeptat a temperature of .50 C

1The.niixture-atlfirstturbid, very. quicklyi'be comes clean TThe.yildofi ester .obtained is after? hours, 92.9;per,cent..of,ester at50",(3.;

, after further. 4. hours,.94.6 percent. of este r Q at 50C.; afterfurther 1& hours, 97.0 per I 10. The new process which comprisesactesters of borneol by causing cent of ester at room temperature; corresponding to an esterification of 100 per cent.

1) If the process is carried out as described in Example 3, but withoutheating the mixture, at ordinary temperature, the following yields ofester are obtained: after 1 hour, 7 6.6 per cent. of ester; after afurther hour 84.6 per cent. of ester; after further 4 hours, 92.3 percent. of ester; after further l mours, 95.3 per cent. of ester;corresponding to an esterification of 97.3 per cent.

' In the following the term borneol is intended toinclude likewiseisobo'rneol which is an obvious chemical equivalent thereof. Y

I claim:

.' 51'. In. the process of preparing esters of borneol by causing fattyacids to fatty acid In'test mony whereof, I aflizi my signature.

VALENTIN HILOKEN.

react upon camphene, the new step which consistsin adding a small amountof borontrifluoride to the reaction mixture.

2. In the pr'ocess of preparing fatty acid fatty acids to react uponcamphene, the new step which consists in adding a small amount ofborontrifluoride of about 0.3 to

1 per cent,calculated upon the amount of camphene, to the reactionmixture. I

3. The new process which comprises reacting at ordinary temperature withfatty acids upon camphene in -the presence of a small amount ofborontrifluoride.

4. The new process which comprises reacting at ordinary temperature withfatty acids upon camphene in the presence of a small amount-ofborontrifluoride of about 0.3 l

to 1 per cent; calculated upon the amount of camphene 5. The new processwhich comprises re acting at ordinary temperature with lower fatty acidsupon camphene in the presence '1 "of a small amount of borontrifluoride.

6. The new process which comprises reactto 1 per cent, calculated uponthe amount of camphene.

7 Thenew pro cess which comprises causing at ordinary temperaturewithlowerfatty acids upon, camphene in the presence of a small amount ofborontrifluoride of about 0.3

ing lower fatty acids in a small excess to act upon camphene in thepresence of a small amount of borontrifluoride.

8. The new process which comprises reacting with lower fatty acids inan'excess of about 20 per cent. over the theoretical amount uponcamphene in j 9. The new process whichcomprisesreact- 1y raisedtemperature of about 50C.

the presence of a small amount of borontrifluoride. i 60 3 'ing with thetheoretical j'fatty acid upon camphene in the presence of a small amountof borontrifluoride ata slight- 1 w amount of a lower

